In the application of paints and lacquers to automobile bodies and other types of articles it is customary to carry out such operations in enclosed spray booths and to introduce into such spray booths a curtain of water to wash the air and to remove over-sprayed paints or lacquer solids. The water containing suspended solids is filtered or otherwise treated to separate the solids so that the water can be recycled.
The paint and lacquer solids, which are washed away and form suspension in the water that is removed from the spray booths present a disposal problem. In order to avoid contamination of the environment it is customary to separate these solids from the water and to recirculate the water. These solids are difficult to separate by the usual methods of filtration.
This process involves many problems. Thus, the paint and lacquer solids are normally tacky and tend to adhere to the walls, ceilings and floors of the spray booths which makes it necessary to shut down the operation from time to time in order to clean the spray booths. The deposits which are formed on the walls, ceilings and floors of the spray booths are also subject to the growth of anaerobic corrosive bacteria (e.g., Desulfovibrio) which generate corrosive and highly objectional hydrogen sulfide.
Recently, chemical compositions have been provided which when added to the water used to wash the air and to remove over-sprayed paints and lacquers will detackify the paint and lacquer particles. These chemical compositions usually consist of a blend of water-soluble salt of an amphoteric metal and a polycationic water dispersible polymer, and are more fully disclosed in U.S. Pat. No. 3,861,887 which is hereinafter incorporated by reference.
While these compositions have generally been effective in detackifying and removing over-sprayed paint, there has been a serious need to increase the efficiency of this process so that the booths can remain in longer use before normal cleaning operations and allow a better quality of waste water to be discharged from the washing operations. It would, therefore, be desirable to increase the operational efficiency of these blends so as to shorten the time necessary for the removal of paint and lacquer sludge and to increase productivity.